I recently picked up Graves jungle, and even though I tend to have good kda, damage, objective damage etc. in most games, I just can't carry with him unlike I could with my previous main champs (Warwick, Jax). To carry the worst baddies this game you need a champ which can go 1v5, Graves lacks the mobility that's needed.
When I play Warwick and enemy doesn't focus me, I can kill them all or at least win the fight and make them flee. If they focus me, my team can at least get enough damage since it takes so long time to kill me. Same with Jax, R and E make me really hard to kill but a Jax can't be left unfocused either.
So advice to ones looking to carry up the ladder: pick a champ which can 1v5 so you can drag your r3tarded team on your back. For me it seems to be a bruiser with high damage, durability and mobility. Maybe something else can work too, e.g. reset assassins like Kat or Akali.